Flash synchronizing device

ABSTRACT

Flash synchronizing device of a photographic camera having an automatic exposure control device and a programming shutter for synchronizing a flash bulb used with the camera so as to obtain the proper exposure. The device comprises M-contacts coupled with the shutter so as to be closed at about the moment the shutter blades begin to be opened, and a variable resistor connected to the automatic exposure control device of the camera and coupled with a distance setting ring of the camera so that the resistance of the variable resistor is varied as the distance set in the distance setting ring is varied. The resistance characteristics of the variable resistor is so determined that the aperture of the programming shutter is increased by the resistance of the variable resistor beyond the aperture normally obtainable by the automatic exposure control device thereby permitting the decrease in the light quantity received through the shutter due to the non-synchronization of the peak of radiation of the flash bulb with the full aperture of the shutter controlled by the automatic exposure control device to be compensated for to attain the proper exposure.

United States Patent Matsuzaki 1 May 8, 1973 [54] FLASH SYNCHRONIZINGDEVICE [5 7] 7 ABSTRACT {75] inventor: Soichiro MatsuzakLTokymE Pa Flashsynchronizing device of a photographic camera having an automaticexposure control device and a [73] Asslgnee' gnympus optical Tokyoprogramming shutter for synchronizing a flash bulb apan used with thecamera so as to obtain the proper expo- [22] Filed: Apr. 21, 1971 sure.The device comprises M-contacts coupled with the shutter so as to beclosed at about the moment the [211 App! 135927 shutter blades begin tobe opened, and a variable resistor connected to the automatic exposurecontrol [52] U.S.Cl. ..95/10 CE, 95/ll.5 R, 95/64 A device of the cameraand coupled with a distance [51] Int. Cl. ..G03b 7/16 setting ring ofthe camera so that the resistance of the [58] Field of Search ..95/l0 C,10 CE, 10 CT, variable resistor is varied as the distance set in the95/10 CD, 64 A, 11.5 R distance setting ring is varied. The resistancecharacteristics of the variable resistor is so determined that [56]References Cited the aperture of the programming shutter is increased bythe resistance of the variable resistor beyond the UNITED STATES PATENTSaperture normally obtainable by the automaticexpo- 3,392,643 7/1968Rentschler ..95/64 A u C ntr l device thereby permitting the decrease in3,422,738 1/1969 Mori et al ..95/1O CT the light quantity receivedthrough the shutter due to 3,504,602 4/1970 Kiper et al. ..95/11.5 R thenon-synchronization of the peak of radiation of Rentschler A the flashthe aperture of the hutter con- Primary Examiner-Samuel S. MatthewsAssistant Examiner-Russell E. Adams, Jr. Attorney-Kelman & Bermantrolled by the automatic exposure control device to be compensated forto attain the proper exposure.

4 Claims, 26 Drawing Figures CdS FLASH SYNCHRONIZING DEVICECross-Reference to Related Application U.S. Ser. No. 90,289 entitledPRCGRAMMING SHUTTER FOR A PHOTOGRAPHIC CAMERA" which was filed on Nov.17, 1970, now US. Pat. No. 3,643,562, discloses the mechanicalconstruction of the programming shutter used in this application.

BACKGROUND OF THE INVENTION The present invention relates to a flashsynchronizing device of a photographic camera having an automaticexposure control device and a programming shutter provided with shutterblades which serve also as diaphragm blades the aperture of which variesso as to attain the proper exposure by means of the automatic exposurecontrol device.

In a photographic camera provided with a programming shutter of the typedescribed above, the amount of movement of the shutter blades isautomatically controlled by the automatic exposure control device sothat the aperture is varied so as to obtain the proper exposure.

Therefore, it is made difficult to synchronize a flash device coupledwith the camera over the entire range of the shutter time. Thus, theflash photography using the synchronizing M-contacts of the camerahaving a programming shutter has been carried out by setting the shuttertime at a low speed and by utilizing a diaphragm additionally mounted onthe shutter, thereby unavoidably losing the advantages of theprogramming shutter.

Since shutter blades of a programming shutter are opened at a relativelylow speed and closed rapidly at the moment an aperture for the properexposure is attained, the X-contact synchronization of a flash device byusing X-contacts can be effected if the X-contacts are closed at amoment when the movement of the shutter blades for opening the same isswitched to that for closing the shutter blades or at a moment veryclose thereto. This can be easily carried out by utilizing, for example,a shutter blade actuating member such as a rotary disc operably coupledwith the shutter blades which is energized by the film winding operationand rotated one revolution by the releasing of the shutter so as to openthe shutter blades during the preceding half revolution of the disc andclose the same during the succeeding half revolution of the disc and bylocating the X-contacts at a position near the disc at which theX-contacts are closed by a projection formed in the disc when the discrotates the preceding half revolution.

Thus, the X-contacts are closed at the moment when the shutter bladeshave been opened for the proper exposure by the automatic exposurecontrol device and the movement of the shutter blades is switched forthe closing movement thereof.

ln order to properly operate the automatic exposure control device in aflash photography by using a flash device coupled with the camera, avariable resistor may be used in place of a photoelectric elementprovided in the automatic exposure control device for controlling themovement of the pointer of a galvanometer or the reference time obtainedfrom the time constant setting CR circuit in the automatic exposurecontrol device which variable resistor is coupled with a distancesetting ring of the camera so that the resistance of the variableresistor is varied correspondingly to the distance set in the distancesetting ring thereby permitting the movement of the pointer or thereference time to be controlled by the resistor.

However, when M-contacts of the camera are used for the synchronizationof a flash bulb coupled with the camera which requires a relatively longtime such as l5 to 20 milliseconds (ms) until the peak or the maximumintensity of the radiation of the flash bulb is attained from the timeof ignition of the bulb and in which the duration of the radiation isrelatively long, the M-contacts must be closed at a time about 15 to 20ms before the shutter blades are opened to attain an aperture for theproper exposure so that the peak of radiation of the flash bulbsynchronizes with the full aperture of the shutter blades obtained bythe automatic exposure control device for the proper exposure.

Since the time required for opening the shutter blades of a programmingshutter to attain an aperture for the proper exposure varies dependingupon the conditions of exposure, the time at which the M-contacts are tobe closed for synchronizing the peak of radiation of a flash bulb withthe full aperture of the shutter blades for the exposure must be varieddepending upon the condition of the exposure.

It is very difficult and troublesome to incorporate in aprogramming-shutter such a means for determining the time the M-contaetsare to be closed for synchronizing the peak of radiation of a flash bulbwith the full aperture of the shutter blades for the proper exposure.

The present invention aims at solving the above described difficultiesin the prior art flash synchronizing device. 7

SUMMARY OF THE INVENTION The object of the present invention is theprovision of a novel and useful flash synchronizing device of aphotographic camera having an automatic exposure control device and aprogramming shutter which avoids the disadvantages of the prior artflash synchronizing device.

The above object is achieved in accordance with the present invention bythe provision of a flash synchronizing device comprising'M-contactsadapted to be closed at a fixed time at which the shutter blades of theprogramming shutter commence to open or at a time close thereto and avariable resistor incorporated in the automatic exposure control deviceso as to control the movement of the pointer of a galvanometer or thereference time obtained by the RC circuit in the autornatic exposurecontrol device and coupled with a distance setting ring of the camera sothat the resistance thereof is varied in accordance with the setting ofthe distance in the distance setting ring thereby permitting the fullaperture of the shutter blades obtainable by the automatic exposurecontrol device to be varied in accordance with the distance set in thedistance setting ring, the resistance characteristics of the variableresistor being so determined that the movement of the pointer of thegalvanometer or the reference time obtained by the RC circuit arecontrolled in the sense that the full aperture of the shutter bladesobtainable by the automatic exposure control device is increased as thedistance set in the distance setting ring is increased beyond apertureto be given normally by the automatic exposure control device if thepeak of radiation is synchronized with the full aperture of the shutterblades, thereby permitting the reduction in the quantity of lightreceived through the shutter resulting from the fact that the peak ofradiation of the flash bulb is not synchronized with the full apertureof the shutter blades to be compensated for to obtain the properexposure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing therelationship between the time and the aperture of the shutter blades ofa programming shutter;

FIG. 2 is a diagram showing the synchronization of the peak of radiationof a flash bulb with the full aperture of the shutter blades of aprogramming shutter under a first condition of scene brightness;

FIG. 3 is a diagram similar to FIG. 2 but showing the synchronizationunder another condition of the scene brightness;

FIG. 4(a) is a diagram showing the relationship between the radiation ofa flash bulb and the aperture of the shutter blades of the presentinvention with respect to the lapse of time, the chain line showing theaperture of the shutter blades of the prior art while the full lineshows the aperture obtained by the present invention;

FIG. 4(1)) is a diagram showing the variable resistor of the presentinvention set at the point corresponding to the adjustment of thedistance setting ring at. a distance;

FIG. 4(c) is a diagram showing the amount of movement of the pointer ofthe galvanometer in the automatic exposure control device defining thefull aperture of the shutter blades, 0, being the angle obtained by thepresent invention while 0,, is the angle normally obtained by the priorart automatic exposure control device;

FIG. 4(d) is a diagram showing the aperture of the programming shutter,the full line showing the aperture obtained by the present inventionwhile the chain line shows the aperture obtained by the prior artprogramming shutter;

FIG. 5(a) to 5(d) are diagrams similar to FIGS. 4(a) to 4(b),respectively, but showing the positions under another condition of theadjustment of the flash synchronizing device;

FIG. 6(a) to 6(d) are diagrams similar to FIGS. 4(a) to 4(d),respectively, but showing the positions under a still other condition ofthe adjustment of the flash synchronizing device;

FIG. 7 is a wiring diagram showing the electric circuit of an embodimentof the flash synchronizing device of the present invention;

FIG. 8 is a diagram showing various types of the distancecharacteristics of the variable resistor incorporated in the flashsynchronizing device of the present invention to be selected inaccordance with the construction of the automatic exposure controldevice and the programming shutter to be used therewith;

FIG. 9 is a wiring diagram showing the electric circuit of anotherembodiment of the flash synchronizing device of the present invention;

FIG. 10 is a perspective view showing the camera incorporating the flashsynchronizing device of FIG. 9;

FIG. 11 is a fragmentally perspective view showing an embodiment of theshutter blade actuating mechanism in the programming shutter of thepresent invention;

FIG. 12 is a fragmentary plan view showing the'arrangement of X-contactsand M-contacts relative to the rotary disc of the shutter bladeactuating mechanism of FIG. 11;

FIG. 13 is a schematic perspective view of the arrangement of anembodiment of the variable resistors shown in FIG. 9 with respect to thedistance setting ring;

FIG. 14 is a diagram showing an alternative form of the variableresistor used in the electric circuit of the flash synchronizing deviceof FIG. 9 for adjusting the guide number of the flash device coupledwith the camera;

FIG. 15 is a fragmentary sectional view showing the normally openedswitches provided in the accessory shoe mounted on the camera of FIG. 10for attaching the flash device;

FIG. 16 is a wiring diagram of the electric circuit of an alternativeform of the flash synchronizing device of the present invention; and

FIG. 17 is a fragmentary wiring diagram showing another form of theflash synchronizing device of FIG. 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1showing the variation in the aperture of the shutter blades of aprogramming shutter in the ordinate, while the abscissa shows the lapseof time,

the aperture increases along a straight line 0 at a relatively low speedand, when the aperture reaches a value for the proper exposure asdetermined by the automatic exposure control device as indicated by a,b, c, respectively, for example, the shutter blades are rapidly closedas indicated by lines aXa, bXb, cXc, respectively. 7 Therefore, whenWHEN X-contact synchronization of the flash device is desired, itsuffices to close the X- contacts at the point a, b, c, or at a pointvery close thereto, i.e., at the moment the shutter blades begin to beclosed or closely before or after that moment, because the intensity ofthe flash light reaches instantaneously the maximum intensity or thepeak. This can be effected by using a rotary disc in the shutter bladeactuating mechanism as described previously.

However, when M-contact synchronization of a flash bulb having arelatively longtime D such as 15 20 ms, for example, until the intensityof the light reaches the peak from the time of ignition of the flashbulb is desired, the time of ignition of the flash bulb must be changeddepending upon the aperture a, b, c That is, when the M-contactsynchronization is to be effected under the condition of the aperture 0,the time for igniting the flash bulb must be at the time Ma whichprecedes the time Xa by the time D. Similarly, the time for ignitionmust be set at the time Mb which precedes the time Xb by the time D,when the synchronization is to be effected by the aperture 12, and soon. FIGS. 2 and 3 show the condition of the synchronization describedabove in which the peak of radiation of the bulb coincides with the fullaperture of the shutter blades, respectively. This is, however, verytroublesome in practice and requires a ver complicated mechanism in theshutter.

In accordance with the present invention, the time of ignition of theflash bulb in the M-contact flash synchronization is fixedly set at themoment the shutter blades begin to be opened or very close thereto andthe full aperture of the shutter blades obtained by the automaticexposure control device is increased by using a variable resistorconnected in the automatic exposure control device and coupled with adistance setting ring of the camera in comparison with the aperturenormally obtainable by the automatic exposure control device for theproper exposure.

The variable resistor provided in the automatic exposure control deviceis coupled with the distance setting ring so as to vary the resistancethereof in accordance with the distance set in the distance setting ringso that the indication of the galvanometer in the automatic exposurecontrol device or the reference time obtained by the CR circuit or timeconstant setting circuit in the automatic exposure control device isvaried depending upon the distance set in the distance setting ring. Theresistance characteristics of the variable resistor is so determinedthat the full aperture of the shutter blades obtained by the automaticexposure control device is excessively increased by the provision of thevariable resistor in comparison with the aperture normally obtainablewhen the synchronization of the peak of the bulb with the full apertureis attained.

FIGS. 4(a) to 4(d), 5(a) to 5(d) and 6(a) to 6(d) show the manner howthe proper exposure is obtained by the present invention under variousapertures of the shutter blades.

In FIG. 4(a), the aperture indicated by the hatched area is increasedbeyond the area shown by the chain line. FIG. 4(b) shows the adjustmentof the variable resistor coupled with the distance setting ring. FIG.4(0) shows the angle 6, of movement of the pointer of the galvanometerin the automatic exposure control device which is made greater by virtueof the resistance characteristics of the variable resistor than theangle 0,, which is normally obtained in the M-contact synchronization ofthe flash bulb. FIG. 4(d) shows the aperture indicated by the hatchedarea which is obtained by the present invention. This aperture is madegreater than the aperture shown by the chain line which is obtainable bythe normal M-contact synchronization of the flash bulb. FIGS. 5(a) to5(d) and 6(a) to 6(d) show the above facts in various full apertures.

FIG. 7 shows an embodiment of the electric circuit of the flashsynchronizing device of the present invention. It comprises an electricsource E, a photoelectric element CdS and a galvanometer G connected inseries to the electric source E, resistors r, and r representing theinternal resistance of the galvanometer G and a protective resistor forthe galvanometer G, respectively. A variable diaphragm T is located infront of the photoelectric element CdS so as to adjust the device inaccordance with the sensitivity of the film used. The above describedcircuit forms a conventional automatic exposure control device, and theshutter blades are opened to an aperture determined by the movement ofthe pointer of the galvanometer G for the proper exposure.

A variable resistor R having movable contact I, is connected in parallelto the galvanometer G through a switch S, so that the device is adjustedin accordance with the guide number of the flash device coupled with thecamera.

Another variable resistor R which has been described previously isconnected in parallel to the photoelectric element CdS through a switchS which is coupled with the switch S so as to be opened and closedtherewith. The resistor R is coupled with the distance setting ring (notshown) so as to vary the resistance thereof according to the distanceset in the distance setting ring. As previously described, theresistance characteristics of the resistor R is so set that the fullaperture of the shutter blades is increased.

The plus terminal of the electric source E is grounded to the body ofthe camera.

M-contacts M are connected in series to the socket F for receiving theflash device. The M-contacts M are closed by the shutter blade actuatingmechanism at the time the shutter blades begin to be opened or at a timevery close thereto.

In operation of the device described above in M-contact synchronizationof the flash bulb, the switches S 8;. are first closed and the variableresistor R is adjusted for the guide number of the flash bulb mounted onthe socket F. Then, the distance setting ring is operated so as to setthe distance between the camera and the object.

The current flows from the electric source E through the galvanometer Gand the resistor R. Thus, the current is controlled by the resistancechracteristics of the resistor R so that the pointer of the galvanometerG is regulated so as to make the aperture of the shutter blades largerthan that normally obtained by the conventional automatic exposurecontrol device.

Therefore, when the shutter is released, the shutter blades begin to beopened to attain an excessively large aperture while the bulb is ignitedto attain the peak of radiation thereof after a relatively long timesuch as l5 20 ms so that the proper exposure is obtained by virtue ofthe excessively large aperture even though the peak of the bulb does notsynchronize with the full aperture of the shutter blades.

In daylight exposure, the switches S S are opened so that thephotoelectric elementCdS operates in the conventional manner to obtainthe proper exposure.

The resistance characteristics of the variable resistor R are selectedappropriately as shown by (I), (II) in FIG. 8 depending upon theconstruction of the automatic exposure control device and the shutterblade actuating mechanism of the shutter.

In the above description, the M-contacts M are described as being closedat a fixed time. However, the M-contacts M may be closed by theoperation of a link mechanism coupled with the shutter blade actuatingmechanism, in which case the time of closure of the M- contacts isshifted a little amount from the above fixed time.

FIG. 9 shows the electric circuit of another embodiment of the flashsynchronizing device of the present invention. The electric circuit ofFIG. 9 is substantially similar to that shown in FIG. 7 except thatX-contact synchronizing mechanism and a special accessory shoe forautomatically closing the switches 8,, S upon attachment of anelectronic flash device thereto are incorporated therein.

As shown in FIG. 9, a variable resistor R is connected in parallel tothe variable resistor R with one end of each of the resistors R,,, Rbeing connected to the switch S through a selector switch S and a switchS is connected to the M-contacts M while X-contacts X are connected inparallel to the M-contacts M through the switch S The switch S iscoupled with the selector switch 8., so that, when the latter isswitched to connect the variable resistor R in the circuit, the switch Sis closed, while the same is opened when the selector switch S isswitched to connect the variable resistor R in the circuit. The variableresistor R is coupled with the distance setting ring so that theresistance of the resistor R is varied correspondingly to the distanceset in the distance setting ring thereby permitting the aperture of theshutter blades to be controlled to obtain the proper exposure inaccordance with the distance set in the distance setting ring when theswitch S is switched to connect the resistor R in the circuit and theX-contacts are closed at the moment the shutter blades are opened toattain the aperture controlled by the device of FIG. 9.

In this embodiment a plurality of resistors R R and R each havingdifferent resistance and connected in parallel to each other areconnected in parallel to the galvanome ter G through the switch S and arotary selector switch S in place of the variable resistor R in FIG. 7so as to adjust the electric circuit for the guide number of the flashdevice coupled with the camera.

A synchronizing socket S0 and an accessory shoe HS are connected inparallel as shown. The accessory shoe HS is provided with a pair ofpusher pins 2, 3 (FIG. and the switches S and S are located beneath therespective pusher pins 2,-3 as shown in FIG. so that, when the flashdevice is attached to the shoe HS, the switches S S are automaticallyclosed so as to be ready for the flash photography.

FIG. 10 shows a camera incorporating the device of FIG. 9. Knob 4 iscoupled with the rotary selector switch 8;, so that the adjustment forthe guide number is effected by operating the knob 4. A movable lug 6 isprovided in the lens barrel of the objective lens and is coupled withthe selector switch 5., so that either one of the resistors R R isconnected in the circuit by operating the lug 6 for the X-contact or theM-contact synchronization. When the resistor R is connected in thecircuit, the switch S is also closed for connecting the M-contacts M inthe circuit. A rotatable ring 5 in the lens barrel iscoupled with thediaphragm T so as to control the light received by the photoelectricelement CdS so that it is adjusted for the sensitivity of the film used.

The distance setting ring is shown by the numeral 7 and contacts RC andR,. are secured to the ring 7 as shown in FIG. 13. The resistors R and Rare formed by arcuate segments RA and RA made of electrically resistivematerial and secured to a stationary ring 8 in positions correspondingto the contacts R C and RC, respectively. Arcuate electricallyconductive segments RB and RB are secured to the stationary ring 8 alongthe resistance segments R,,A and RA, respectively, and the contacts R,,Cand R are adapted to slidably contact the segments R A, RB and RA, RB,respectively, so

that the resistances given by the resistors R and R can be varied as thedistance setting ring 7 is rotated.

The X-contacts X and the M-contacts M are closed by the shutter bladeactuating mechanism of the aforementioned earlier application as shownin FIGS. 11 and 12. The shutter blade actuating mechanism comprises arotary disc 10 having a projection 10a at its periphery which isenergized to rotate in the anticlockwise direction by a spring 9 whenthe shutter is charged. The disc 10 is releaseably held in its energizedposition by arresting lever 14 rotatable about axis 15 which isdisengaged from the projection 10a of the disc 10 when shutter releasemeans (not shown) is actuated. The disc 10 is provided with an actuatingrod 11 secured thereto which slidably engages with a slot formed at thebent end of a swingable lever 13 rotatable about axis 12. A pin issecured at the other end of the lever 13 which is coupled with shutterblade actuating member (not shown). Thus, when the disc 10 is rotated byone revolution by the releasing action of the shutter, the lever 12 isswung in the clockwise direction during the first halfrevolutionofthedisc l0 andswung back to its initial position during the succeedinghalf revolution of the disc 10 so that the shutter blades (not shown)are opened duringthe first half revolution of the disc 10 while they areclosed during the. succeeding half revolution of the disc 10.

As shown in FIGS. 11 and 12, the M-contacts M are I located adjcent tothe projection 10a of the disc 10 in advance in the direction ofrotation of the disc 10 so as to be closed by the projection 10a atabout the beginning of rotation of the "disc 10 while the X-contacts Xare located at a position at which the X-contacts X are closed by theprojection 10a when the disc 10 rotates about a half revolution from theinitial position thereof. That is, M-contacts M are closed at about thebeginning of the opening movement of the shutter blades while theX-contacts X are closed at about the moment the opening movement of theshutter blades is terminated and the closing movement of the samebegins. I

In operation for the M-contact synchronization of a flash bulb, the lug6 of the camera is moved to switch the switch S to connect the resistorR in the circuit while the switch S is closed, and the ring 5 isoperated to adjust for the sensitivity of the film in the camera. Then,a flash device having a flash bulb is attached to the shoe HS, so thatthe switches S and S are automatically closed for the flashsynchronization. The knob 4 is operated to adjust for the guide numberof the flash bulb.

After the shutter is charged and the distance setting ring 7 isadjusted, the shutter is released so that the M- contact flashsynchronization is effected for the proper exposure.

When X-contact synchronization is desired the switch 4 is switched toconnect the resistor R for the X-contact synchronization by theoperation of the lug 6 and the flash device is replaced by an X-contactflash device. The operation is similar to that of M-contactsynchronization.

The resistors R to R may be replaced by a resistor I having movablecontacts 1 and 1 as shown in FIG. 14 so that the sensitivity of the filmcan also be set in the camera.

FIG. 16 shows a still further embodiment of the flash synchronizingdevice of the present invention.

In this embodiment, the electric circuit of the automatic exposurecontrol device includes a time constant setting RC circuit in place ofthe galvanometer G of FIGS. 7 and 9 for determining the reference timefor controlling the shutter blades for the proper exposure.

The resistance of a photoelectric element such as a CdS element variescorrespondingly to the intensity of light received thereby when theintensity of the light varies gradually. However, if the photoelectricelement is illuminated by a light such as that emanating from a flashlamp the intensity of which varies suddenly, the resistance of thephotoelectric element can not vary instantaneously in response to thevariation in the intensity of the light received by the photoelectricelement thereby resulting in a certain time lag to attain the resistancecorresponding to the intensity of light received.

Therefore, the aperture of the programming shutter controlled by theautomatic exposure control device tends to be made excessively largewhen a flash device is used, thereby resulting in an overexposure. Thistendency of the overexposure is not so serious when the distance betweenthe object and the camera is great. However, if the distance is small,the tendency of the overexposure due to the time lag of the variation inthe resistance of the photoelectric element in response to the rapidvariation in the intensity of light received thereby becomes serious,and a significant overexposure will be obtained.

The embodiment of FIG. 16 avoids the above described overexposure by theprovision of a variable resistor connected in parallel to thephotoelectric element of the automatic exposure control device, whichvariable resistor is coupled with the distance setting ring of thecamera so that the resistance thereof is varied correspondingly to thedistance set in the distance setting ring thereby permitting theoverexposue in the flash photography to be avoided by virtue of theresultant resistance of the photoelectric element and the variableresistor.

In FIG. 16, a photoelectric element CdS and a capacitor C are connectedin series so as to form a timing circuit or a time constant setting CRcircuit. The ends of the capacitor C are connected to the input of aswitching circuit Z of the programming shutter. The switching circuit isconventional, and an electric source B connected to the switchingcircuit Z supplies the power thereof to the timing circuit and theswitching circuit 2. The terminals of the electric source B are alsoconnected to a flash device through a switch S In accordance with thefeature of the present invention, a plurality of resistors r r and reach having a different resistance are connected at their one ends toone end of the photoelectric element CdS while the other ends areconnected to the other end of the photoelectric element CdS through arotary switch S and a normally opened switch S so that either one ornone of the resistors r r r can be selectively connected in parallel tothe photoelectric element CdS by closing the switch S and operating theswitch S As in the case of the embodiment of FIG. 9, the switches S andS may be automatically closed by attaching the flash device to theaccessory shoe of the camera.

The switch S is coupled with the distance setting ring of the camera sothat the selected one or none of the resistors r r r is connected to thephotoelectric element CdS depending upon the distance set in thedistance setting ring. The resistance of each of the resistors r r and ris so determined that the resistance of the resistor connected to thephotoelectric element CdS is made smaller correspondingly to thedistance as the distance set in the distance setting ring is madeshorter. When the distance set in the distance setting ring is madesubstantially great, any of the resistors r r r is disconnected from thecircuit so as to achieve the normal automatic exposure control.

In operation of the flash photography at a relatively short distance,the current is applied to the capacitor C through the resultantresistance of the photoelectric element CdS and the resistor connectedin parallel thereto which is smaller than the resistance of thephotoelectric element CdS per se so that the reference time or the timeconstant set by the timing circuit consisting of the photoelectricelement CdS and the capacitor C is made small in comparison with thetime constant normally obtained when the resistor r r or r is notconnected, so that the overexposure is positively avoided.

FIG. 17 shows an alternative form of the variable resistor connected tothe photoelectric element CdS. The variable resistor r is connected inparallel to the photoelectric element CdS through the switch S Theresistor r is coupled with the distance setting ring so as to vary itsresistance in accordance with the distance set in the distance settingring. The operation of the embodiment of FIG. 17 is similar to that ofFIG. 16.

Iclaim:

1. In a photographic camera having a movable distance setting element,an electrically operated automatic exposure control device, aprogramming shutter controlled by said device, said shutter havingblades adapted to be opened to form an aperture, said aperture beingvaried by said device forobtaining proper exposure, whereby the shutterblades serve as a diaphragm, and flash synchronizing means, theimprovement in the flash synchronizing means which comprises:

a. M-contacts for a flash bulb;

b. coupling means coupling said M-contacts with said shutter for closingsaid M-contacts substantially at the same time said shutter blades beginto be opened;

0. a first variable resistor;

. motion transmitting means operatively interposed between said firstvariable resistor and said distance setting element for varying theresistance of said first variable resistor in response to move ment ofsaid distance setting element;

e. circuit means including first switch means for connecting said firstvariable resistor with said exposure control device and for therebyincreasing said aperture in response to an increase in the distance forwhich said distance setting element is set;

f. X-contacts for an electronic flash device;

g. coupling means coupling said X-contacts with said shutter for closingsaid X-contacts when said shutter blades begin to be closed after havingbeen opened;

h. a second variable resistor} motion transmitting means operativelyinterposed between said second variable resistor and said distancesetting element for varying the resistance of said second variableresistor in response to movement of said distance setting element; j.selector switch means for alternatively connecting said first and secondvariable resistors to said automatic exposure control device when saidfirst switch means is closed; k. third switch means in circuit with saidM-contacts and movable between a contact-operating and acontact-inactivating position in which said third switch means make saidM-contacts operative and inactive respectively; and I coupling meanscoupling said third switch means to said selector switch means formoving said third switch means into the contact-operating positionthereof when said selector switch means connects said first variableresistor to said automatic exposure control device, and for moving saidthird switch means into the contact-inactivating position when saidselector switch means connects said second variable resistor to saidautomatic exposurecontrol device.

2. In a camera as set forth in claim I, wherein said exposure controldevice includes a photoelectric element and a galvanometer in circuitwith said photoelectric element, said galvanometer having a pointermoving in response to light sensed by said photoelectric element andconnected to said shutter for controlling said aperture, said firstvariable resistor being arranged in parallel circuit with saidphotoelectric element through said first switch means.

3. In a camera as set forth in claim 1, a further variable resistor,means for varying the resistance of said second variable resistor inaccordance with the guide number of a flash device to be coupled withsaid camera, further switch means for selectively connecting saidfurther variable resistor in circuit with said automatic exposurecontrol device and for thereby adjusting said automatic exposure controldevice for said guide number, and means coupling said first and furtherswitch means for joint opening and closing.

4. In a camera as set forth in claim 1, a plurality of resistors ofdifferent respective resistances, second switch means and selectorswitch means interposed in series circuit between said resistors andsaid automatic exposure control device for selectively connecting eachof said resistors to said automatic control device, and for therebyadjusting said aperture in response to the setting of said selectorswitch means, means for setting said selector switch means in accordancewith the guide number of a flash device to be coupled to the camera, andcoupling means coupling said first and second switch means for jointopening and closing.

1. In a photographic camera having a movable distance setting element,an electrically operated automatic exposure control device, aprogramming shutter controlled by said device, said shutter havingblades adapted to be opened to form an aperture, said aperture beingvaried by said device for obtaining proper exposure, whereby the shutterblades serve as a diaphragm, and flash synchronizing means, theimprovement in the flash synchronizing means which comprises: a.M-contacts for a flash bulb; b. coupling means coupling said M-contactswith said shutter for closing said M-contacts substantially at the sametime said shutter blades begin to be opened; c. a first variableresistor; d. motion transmitting means operatively interposed betweensaid first variable resistor and said distance setting element forvarying the resistance of said first variable resistor in response tomovement of said distance setting element; e. circuit means includingfirst switch means for connecting said first variable resistor with saidexposure control device and for thereby increasing said aperture inresponse to an increase in the distance for which said distance settingelement is set; f. X-contacts for an electronic flash device; g.coupling means coupling said X-contacts with said shutter for closingsaid X-contacts when said shutter blades begin to be closed after havingbeen opened; h. a second variable resistor; i. motion transmitting meansoperatively interposed between said second variable resistor and saiddistance setting element for varying the resistance of said secondvariable resistor in response to movement of said distance settingelement; j. selector switch means for alternatively connecting saidfirst and second variable resistors to said automatic exposure controldevice when said first switch means is closed; k. third switch means incircuit with said M-contacts and movable between a contact-operating anda contact-inactivating position in which said third switch means makesaid M-contacts operative and inactive respectively; and l. couplingmeans coupling said third switch means to said selector switch means formoving said third switch means into the contact-operating positionthereof when said selector switch means connects said first variableresistor to said automatic exposure control device, and for moving saidthird switch means into the contact-inactivating position when saidselector switch means connects said second variable resistor to saidautomatic exposure control device.
 2. In a camera as set forth in claim1, wherein said exposure control device includes a photoelectric elementand a galvanometer in circuit with said photoelectric element, saidgalvanometer having a pointer moving in response to light sensed by saidphotoelectric element and connected to said shutter for controlling saidaperture, said first variable resistor being arranged in parallelcircuit with said photoelectric element through said first switch means.3. In a camera as set forth in claim 1, a further variable resistor,means for varying the resistance of said second variable resistor inaccordance with the guide number of a flash device to be coupled withsaid camera, further switch means for selectively connecting saidfurther variable resistor in circuit with said automatic exposurecontrol device and for thereby adjusting said automatic exposure controldevice for said guide number, and means coupling said first and furtherswitch means for joint opening and closing.
 4. In a camera as set forthin claim 1, a plurality of resistors of different respectiveresistances, second switch means and selector switch means interposed inseries circuit between said resistors and said automatic exposurecontrol device for selectively connecting each of said resistors to saidautomatic control device, and for thereby adjusting said aperture inresponse to the setting of said selector switch means, means for settingsaid selector switch means in accordance with the guide number of aflash device to be coupled to the camera, and coupling means couplingsaid first and second switch means for joint opening and closing.